フェニルブタゾン
Phenylbutazone
Phenylbutazone (synthetic pyrazolone derivative)
別名: Butazolidin · Phenylbute · butadiene · fenilbutazona · phenylbutazonum
VetSheet 獣医チームが監修更新日 2026年4月5日エビデンスに基づく獣医学リファレンス
用量は獣医専門家向けの臨床参考資料です。必ず最新の医薬品情報および個別症例に基づいて確認してください。
動物種別用量
🌎 NA — North America🌍 EU — Europe
犬
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| General inflammation/pain | 14 mg/kg | PO | three times daily initially | — | 🌎 NA |
| General inflammation/pain | 15-22 mg/kg | PO | q12h | — | 🌎 NA |
| Analgesia | 1-5 mg/kg | PO | q8h | — | 🌎 NA |
- General inflammation/pain: Maximum of 800 mg/day regardless of weight; titrate dose to lowest effective dose. Rarely used today.
馬
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| To reduce pain or pyrexia associated with pleuropneumonia | 2.2-4.4 mg/kg | PO or IV | q12h | first week of treatment or longer | 🌎 NA |
| General musculoskeletal inflammation | 1-2 grams per 454 kg (1000 lb.) horse IV, or 2-4 grams per 454 kg (1000 lb.) horse PO | IV or PO | daily | Limit IV administration to no more than 5 successive days | 🌎 NA |
| Adjunctive treatment of colic (to reduce endotoxic effects) | 2.2 mg/kg | PO or IV | twice daily | — | 🌎 NA |
| Adjunctive treatment of laminitis | Initial dose of 4 grams, immediately decreased to 1 to 1.5 grams | PO or IV | twice daily | — | 🌎 NA |
| Osteoarthritis | 2.2 mg/kg | PO | twice daily | — | 🌎 NA |
- General musculoskeletal inflammation: Do not exceed 4 grams/day. Use high end of dosage range initially, then titrate to lowest effective dose. Injection must be made slowly and with care.
- Adjunctive treatment of laminitis: Dose for an average adult-sized horse. Lower dose is used to keep the horse comfortable, but not relieve pain to the extent the horse moves around excessively.
- Osteoarthritis: Minimal dose to control pain.
牛
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| General inflammation/pain | 4-8 mg/kg PO or 2-5 mg/kg IV | PO or IV | — | — | 🌎 NA |
| General inflammation/pain | 10-20 mg/kg PO, then 2.5-5 mg/kg q24h or 10 mg/kg every 48 hours PO | PO | q24h or q48h | — | 🌎 NA |
- General inflammation/pain: Extralabel use prohibited in female dairy cattle 20 months of age or older.
- General inflammation/pain: Extralabel use prohibited in female dairy cattle 20 months of age or older.
豚
| 適応 | 用量 | 経路 | 頻度 | 期間 | 地域 |
|---|---|---|---|---|---|
| General inflammation/pain | 4 mg/kg | IV or PO | q24h | — | 🌎 NA |
| General inflammation/pain | 4-8 mg/kg PO or 2-5 mg/kg IV | PO or IV | — | — | 🌎 NA |
用量は獣医専門家向けの臨床参考資料です。必ず最新の医薬品情報および個別症例に基づいて確認してください。
概要
フェニルブタゾン（通称 "bute"）は、ピラゾロン系の古典的な非選択的非ステロイド性抗炎症薬（NSAID）です。
臨床上のポイント： 歴史的には強力な鎮痛、抗炎症、解熱作用のため多くの動物種で使用されてきましたが、現代の獣医療では、その使用はほぼ馬の臨床における筋骨格系の痛み（蹄葉炎、骨関節炎など）の管理に限定されています。
小動物（犬や猫）では、血液疾患、肝毒性、重度の胃腸潰瘍などの重篤な副作用のリスクが高いため、より安全なCOX-2選択的NSAID（カルプロフェンやメロキシカムなど）にほぼ置き換えられています。ヒトに対する骨髄毒性（再生不良性貧血）の安全上の懸念から、産業動物での使用は厳しく規制されています。
作用機序
Phenylbutazone acts primarily by inhibiting the cyclooxygenase (COX) enzymes (both COX-1 and COX-2), which prevents the conversion of arachidonic acid → prostaglandins and thromboxanes.
- ↓ Prostaglandins → Reduced inflammation, analgesia, and antipyresis.
- ↓ Thromboxane A2 → Decreased platelet aggregation.
Pharmacological Note: Phenylbutazone is metabolized in the liver to oxyphenbutazone, an active metabolite that contributes significantly to its prolonged efficacy (often >24 hours) despite a relatively short plasma half-life. The irreversible binding of phenylbutazone to cyclooxygenase also extends its duration of action. It also possesses mild uricosuric properties.
安全性・警告
禁忌
- Known hypersensitivity to phenylbutazone or other NSAIDs
- History of or preexisting hematologic or bone marrow abnormalities
- Preexisting gastrointestinal ulcers
- Food-producing animals (especially female dairy cattle 20 months of age or older)
- Lactating dairy cattle
- Pre-existing gastrointestinal ulceration
- Renal impairment
- Hepatic impairment
- Hematological disorders
- Use in food-producing animals (banned in many jurisdictions)
有害事象
- Gastrointestinal and oral erosions/ulcers
- Hypoalbuminemia (especially in foals/ponies)
- Renal papillary necrosis and azotemia
- Sodium and water retention (edema)
- Blood dyscrasias (agranulocytosis, aplastic anemia)
- Hepatotoxicity
- Severe tissue necrosis and sloughing (if injected IM or SC)
- CNS stimulation and seizures (if injected intracarotid)
- Gastrointestinal ulceration and bleeding
- Bone marrow suppression (aplastic anemia, leukopenia)
注意事項
Use with extreme caution in foals and ponies due to increased incidence of hypoproteinemia and GI ulceration. Avoid in horses with known or suspected Equine Gastric Ulcer Syndrome (EGUS). Use cautiously in animals with preexisting renal disease or congestive heart failure (CHF) due to potential for sodium/water retention and decreased renal blood flow. May mask clinical signs of lameness in horses. WARNING: Do not administer injectable preparations IM or SC as it is highly irritating and causes necrosis/sloughing. Intracarotid injections may cause CNS stimulation and seizures.
医薬品相互作用
Phenylbutazone may antagonize the increased renal blood flow effects caused by furosemide.
Concurrent administration may increase the chances of hepatotoxicity developing.
Concurrent use increases the potential for adverse GI and renal reactions. (Note: 'Stacking' with ketoprofen shows synergistic toxicity).
May increase the risk of hematologic and/or renal adverse reactions.
Phenylbutazone may increase the plasma half-life of penicillin G.
Phenylbutazone could potentially displace sulfonamides from plasma proteins, increasing the risk for adverse effects.
Phenylbutazone could potentially displace warfarin from plasma proteins, increasing the risk for bleeding.
Increased risk of gastrointestinal ulceration
Increased risk of gastrointestinal ulceration and renal toxicity
Displacement from plasma proteins leading to increased free drug concentrations
監視
- Analgesic, anti-inflammatory, and antipyretic efficacy
- Complete blood counts (CBC) with chronic therapy (weekly early in therapy, biweekly later)
- Urinalysis and renal function parameters (serum creatinine/BUN) with chronic therapy
- Plasma protein determinations (especially in ponies, foals, and debilitated animals)
- Complete Blood Count (CBC)
- Renal function (BUN, Creatinine)
- Liver enzymes
- Clinical signs of GI bleeding (melena)
薬物動態
半減期
吸収
Absorbed from both the stomach and small intestine following oral administration.
分布
Distributed throughout the body with highest levels attained in the liver, heart, lungs, kidneys, and blood. Plasma protein binding in horses exceeds 99%. Crosses the placenta and is excreted into milk.
代謝
Nearly completely metabolized in the liver, primarily to oxyphenbutazone (active) and gamma-hydroxyphenylbutazone.
消失
Excreted primarily in the urine. More rapidly excreted into alkaline than acidic urine. Oxyphenbutazone can be detected in horse urine up to 48 hours after a single dose.
過剰投与
Manifestations of acute overdosage include prompt respiratory or metabolic acidosis with compensatory hyperventilation, seizures, coma, and acute hypotensive crisis.
- Systemic Effects: Clinical signs of renal failure (oliguric, proteinuria, hematuria), liver injury (hepatomegaly, jaundice), bone marrow depression, and severe GI ulceration/perforation may develop.
- Dogs: Common signs include ataxia, seizures, tachycardia, trembling, tremors, vomiting, and tachypnea. Oral LD50 is 332 mg/kg.
- Horses: Common signs include colic, anorexia, and ataxia.
Treatment: Standard overdose procedures should be followed (e.g., empty gut following oral ingestion). Institute supportive treatment as necessary. Intravenous diazepam can be used to help control seizures. Monitor fluid therapy carefully, as phenylbutazone may cause fluid retention.
製品
製剤
- Tablets
- Oral powder
- Oral paste
- Injection
- 100 mg tablet
- 200 mg tablet
動物用医薬品
- Phenylbutazone Tablets: 100 mg, 200 mg, 1 gram
- Phenylbutazone Oral Powder: 1 gram in 10 grams of powder
- Phenylbutazone Paste Oral Syringes: 6 grams or 12 grams/syringe
- Phenylbutazone Injection: 200 mg/mL in 100 mL vials
- 100 mg tablets (Currently unavailable)
- 200 mg tablets (Currently unavailable)
規制ステータス
POM. Licensed forms for small animals are currently unavailable. Prohibited in food-producing animals.
POM-V. Licensed forms for small animals are currently unavailable. Prohibited in food-producing animals.
規制データなし: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
保管・安定性
Oral products should be stored in tight, child-resistant containers if possible. The injectable product should be stored in a cool place (46-56° F) or kept refrigerated.
飼主向け情報
馬の飼い主様へ：
- 「Bute（ビュート）」は骨や関節の痛みの管理に非常に効果的です。必ず獣医師の指示通りに投与してください。
-
重大な警告： 液体の注射剤を筋肉内（IM）または皮下（SC）に絶対に投与しないでください。専門家による静脈内（IV）への厳密な投与が必要です。誤った注射は重度の組織壊死や脱落を引き起こします。
- 胃潰瘍や腎臓の問題の兆候（食欲不振、下痢、疝痛の兆候、脚や腹部の腫れなど）がないか注意深く観察してください。これらの症状が現れた場合は投薬を中止し、獣医師に連絡してください。
犬の飼い主様へ：
- より安全な代替薬があるため、現在この薬が犬に使用されることは稀です。もし処方された場合は、嘔吐、黒色/タール状の便、または無気力がないか非常に注意深く観察し、これらの症状が現れた場合は直ちに獣医師に連絡してください。
産業動物に関する制限：
- FDAにより、生後20ヶ月以上の搾乳牛への使用は厳格に禁止されています。
- 肉牛に適用外使用する場合、厳密な休薬期間が適用されます（例：1回投与＝30日、2回投与＝35日）。獣医師にご相談ください。
VetSheet医薬品リファレンスは獣医専門家の臨床意思決定支援を目的としており、専門的判断または製造業者の最新医薬品情報の代替にはなりません。